Conventionally, there is a certain surveillance camera having two types of modes, a day mode of imaging under illumination of visible light such as natural light in daytime or white light, and a night mode of imaging with emission of the infrared light. With such a surveillance camera, a color image is obtained in the day mode. In contrast, reflected infrared light reflected by a subject is received in the night mode, in which solely the light reception intensity of the reflected light (infrared light) can be obtained and color information such as R, B, and G cannot be obtained. Accordingly, the obtained image is a monochrome image of gray, green, or the like.
In consideration of the use of the surveillance camera, it is desirable that a color image can be obtained also in the night mode. Conventionally, methods have been proposed for generating a color image on the basis of an image obtained by imaging a state in which infrared light is emitted toward an imaging range (subject) (hereinafter referred to as an infrared image).
For example, Patent Document 1 discloses a technique of alternately capturing an infrared image in a state where the infrared light is emitted and a visible image under low illuminance with no emission of the infrared light frame-by-frame so as to generate a color image using the captured images.